Nucleotides downregulate aquaporin 2 via activation of apical P2 receptors

Abstract

Vasopressin regulates water reabsorption in the collecting duct, but extracellular nucleotides modulate this regulation through incompletely understood mechanisms. We investigated these mechanisms using immortalized mouse collecting duct (mpkCCD) cells. Basolateral exposure to dDAVP induced AQP2 localization to the apical membrane, but co-treatment with ATP internalized AQP2. Because plasma membrane-bound P2 receptors (P2R) mediate the effects of extracellular nucleotides, we examined the abundance and localization of P2R in mpkCCD cells. In the absence of dDAVP, P2Y1 and P2Y4 receptors localized to the apical membrane, whereas P2X2, P2X 4, P2X5, P2X7, P2Y2, P2Y 11, and P2Y12 receptors localized to the cytoplasm. dDAVP induced gene expression of P2X1, which localized to the apical domain, and led to translocation of P2X2 and P2Y2 to the apical and basolateral membranes, respectively. In co-expression experiments, P2R activation decreased membrane AQP2 and AQP2-mediated water permeability in Xenopus oocytes expressing P2X2, P2Y2, or P2Y4 receptors, but not in oocytes expressing other P2R subtypes. In summary, these data suggest that AQP2-mediated water transport is downregulated not only by basolateral nucleotides, mediated by P2Y2 receptors, but also by luminal nucleotides, mediated by P2X2 and/or P2Y4 receptors. Copyright © 2009 by the American Society of Nephrology.